The present invention relates generally to the fabrication of semiconductor devices, and more particularly to magnetic random access memory (MRAM) devices.
Semiconductors are used for integrated circuits for electronic applications, including radios, televisions, and personal computing devices, as examples. One type of semiconductor device is a semiconductor storage device, such as a dynamic random access memory (DRAM) and flash memory, which use an electron charge to store information.
A more recent development in memory devices involves spin electrics, which combines semiconductor technology and magnetics. The spin of an electron, rather than the charge, is used to indicate the presence of a xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d. One such spin electronic device is a magnetic random-access memory (MRAM), which includes conductive lines positioned perpendicular Lo one another in different metal layers, the conductive lines sandwiching a magnetic stack. The place where the conductive lines intersect is called a cross-point. A current flowing through one of the conductive lines generates a magnetic field around the conductive line and orients the magnetic polarity into a certain direction along the wire or conductive line. A current flowing through the other conductive line induces the magnetic field and can partially turn the magnetic polarity, also. Digital information, represented as a xe2x80x9c0xe2x80x9d or xe2x80x9c1xe2x80x9d, is stored in the alignment of magnetic moments. The resistance of the magnetic component depends on the moment""s alignment. The stored state is read from the element by detecting the component""s resistive state. A memory cell may be constructed by placing the conductive lines and cross-points in a matrix structure having rows and columns.
An advantage of MRAMs compared to traditional semiconductor memory devices such as DRAMs is that MRAMs can be made smaller and provide a non-volatile memory. For example, a personal computer (PC) utilizing MRAMs would not have a long xe2x80x9cboot-upxe2x80x9d time as with conventional PCs that utilize DRAMs. MRAMs permit the ability to have a memory with more memory bits on the chip than DRAMs or flash memories. Also, an MRAM does not need to be powered up and has the capability of remembering the stored data.
A disadvantage of manufacturing MRAMs is that copper is the preferred material for the conductive lines, due to the excellent conductive properties of copper compared to alumunimum and other conventional metals used in semiconductor technology. Copper oxidizes easily, and additional processing steps are required in order to prevent oxidation. Furthermore, copper cannot be etched, and therefore, damascene processes must be used to form copper conductive lines. Misalignment is a frequent problem with damascene processes, which is particularly problematic in the manufacturing of MRAM devices.
What is needed in the art is an MRAM structure and processing flow method that alleviates the conductive line misalignment problem in prior art MRAM designs.
The present invention achieves technical advantages as an MRAM device having aluminum conductive lines. A process flow that integrates magnetic cross-point devices in an aluminum back-end-of-line (BEOL) without additional lithographic steps is disclosed herein. The process and structure is self-aligned and no additional lithographic masks are needed for a magnetic device application.
Disclosed is an MRAM device comprising a workpiece, a first dielectric layer disposed over the workpiece, and at least one first conductive line disposed over the first dielectric layer. A magnetic stack is disposed over the first conductive line and at least one second conductive line is disposed over the magnetic stack orthogonal to the first conductive line, and the magnetic stack resides between cross-points of the first and second conductive lines.
Also disclosed is a method of manufacturing an MRAM device, comprising providing a workpiece, depositing a first metallization layer over the workpiece. A magnetic stack is deposited over the first metallization layer, and the magnetic stack and first metallization layer are patterned and etched to form first conductive lines. A first dielectric layer is deposited over the magnetic stack and first conductive lines. A planarization, chemical mechanical polish (CMP), for example, process is performed to planarize the dielectric surface and expose the magnetic layer. A second metallization layer is deposited over the first dielectric layer. The second metallization layer and the magnetic stack are patterned and etched to form second conductive lines orthogonal to the first conductive lines, and leave portions of the magnetic stack between cross-points of the first and second conductive lines.
Advantages of the invention include providing a process flow for integrating magnetic cross-point devices in an aluminum BEOL with no additional lithographic steps. The process is self-aligning, which prevents shorts between metallization layers. No additional lithographic masks are needed for MRAM fabrication in accordance with the present invention. The use of copper as metallization layers is avoided with the present invention, so that damascene processes are not required. Aluminum can be etched directly, unlike copper which is unetchable. Thus, the formation of MRAM conductive lines is simplified and requires fewer processing steps.